In an effort to finish the transformation of the Charles River from one of the nation's dirtiest urban rivers to one of the cleanest, the federal government has reached a landmark settlement with the Massachusetts Water Resources Authority (MWRA) requiring the MWRA to implement significant improvements in Boston's sewage collection system.

The agreement, announced on March 15, finalizes a long-term control plan to reduce combined sewer overflows (CSOs) throughout the MWRA system, and is expected to cost MRWA about $20 million yield sharp reductions in storm overflows containing raw sewage to the Charles River. As a result of the new and ongoing efforts, Boston is expected to have among the cleanest river and beach environments of any major urban area in the nation, agency officials said.

Since 1988, the EPA's New England office has taken great strides to help reduce CSO discharges into Boston Harbor and other waterways, including both the Charles River and South Boston beaches. CSOs result from heavy rainfall or snowmelt events that cause surges of wastewater to enter sewer systems that are not equipped to handle the excess amounts, resulting in sewage being directly discharged into nearby waterways. The sewage that CSOs typically carry contains not only stormwater but also untreated human waste, industrial waste, toxic materials and floating debris. The settlement is expected to bring CSO discharges to the Charles River down to approximately eight million gallons per year, from a 1988 level of 1.7 billion gallons. The plan comes on the heels of an earlier agreement that will help make South Boston beaches among the cleanest in the country.

"This settlement represents a monumental step forward in improving water quality in the Charles River and builds upon work to protect South Boston beaches," said Granta Y. Nakayama, EPA's assistant administrator for the Office of Enforcement and Compliance Assurance. "Systems like this across our nation allow significant water pollution to occur. This settlement will ensure the integrity of the local waterways and ensure that the health and environment of Boston's residents are protected."

"The Charles River is a treasured jewel in the crown of a beautiful city, providing Bostonians with great outdoor activities such as sailing, canoeing and rowing," said Robert W. Varney, regional administrator of the EPA's New England office. "With this new commitment, we will better protect people's health and our environment, plus we're even closer to our goal of a Charles River once again safe for swimming on hot summer days."

"(This) settlement builds upon the progress the United States, the state and the MWRA have made in helping to make the Charles River and other local water bodies cleaner and freer from harmful sewage discharges that have polluted their waters for years," said Sue Ellen Wooldridge, assistant attorney general of the Justice Department's Environment and Natural Resources Division. "This landmark settlement will bring much needed protection to human health and the environment and help to restore one of Boston's most valuable natural resources."

Since 1995, the EPA has promoted a "Clean Charles" effort, working closely with other government agencies and private organizations, with the common goal of making the lower Charles River -- from the Watertown Dam to Boston Harbor -- both fishable and swimmable. The Charles is substantially cleaner today than it was in 1995, and the agreement with the MWRA improves upon past actions taken and brings the effort closer to its ultimate goal.

Under the settlement, the MWRA is committing to take a number of actions at the Cottage Farm primary treatment facility. These include:

Using an abandoned 54-inch pipe beneath the Charles River to relieve pressure on the treatment facility during heavy storm events.

Conveying additional flow to the Ward Street Headworks.

Optimizing operations at the Cottage Farm facility (including the interconnection of sewer lines at the facility) to better balance flow.

The MWRA will also perform an engineering evaluation of further system enhancements, including:

Use of real-time controls at a number of overflow regulators.

Modification of existing interconnections to better balance flow in a number of main sewer interceptors.

Evaluation of the construction of new interconnections between two main sewer interceptors in the vicinity of the Charles River.

These controls should result in a dramatic reduction of discharges from Cottage Farm -- including only two discharges per year, and no untreated discharges. Overall, the newly proposed work will eliminate more than two-thirds of the annual volume of wastewater overflows to the Charles that would have been allowed under the previous plan.